-- don't use cruise control. in slippery conditions, you need to be able to ease off the gas quickly, and you can't when your cruise control is on. so that's the mess on the ground but if you are flying up, the air is messy, too. for that part of the story we turn to abc's david kerley at o'hare international airport in chicago. david, good evening. >> reporter: good evening. this is united's o'hare airport command center, the busiest time of the year. over all tonight there are 7200 flights in the air. in atlanta one in three flights was delayed today. there is another map they're interested in in chicago. it's that map sam showed you, the weather map and the storm which could cause huge airline delays. worried about the weather passengers are hitting airports early, but in some cases even that is not enough. >> i actually had a job interview in little rock and i got stuck in houston last night because my flight from little rock was delayed. >> reporter: that's just the start. tomorrow 2.4 million people will fl